I have long thought it has been a mistake to switch to 4-3 this year, we just don't have the DL. More specifically we don't have DEs to get pressure. You MUST get pressure regularly if you are going to run a 4 DL set. CBs are too raw to leave on an island and LBs are not good enough in coverage. Better to have another LB to give different looks, blitz options and/or DB support.
I fully support a 4-3 if you can get pressure from some rush ends.